This invention relates to temperature-controlled apparatus and more particularly to temperature-controlled apparatus for precise control of the permeation of a fluid into a carrier fluid.
It has previously been proposed to provide controlled mixing of one fluid with another by the utilization of diverse types of dilution or proportioning techniques, such as permeation or diffusion. See, for example, U.S. Pat. Nos. 3,521,865; 3,533,272; 3,618,811; 3,209,579; 3,669,637; 2,843,138; 3,516,278; British Pat. No. 811,401; and Review of Scientific Instruments, March, 1955, Vol. 26, No. 3, pp. 305-306. For example, by one method used in calibrating a sulphur dioxide analyzer, a permeation tube containing liquified sulphur dioxide is placed in a heater chamber or conduit through which air, serving as a carrier or dilution gas, is passed. The sulphur dioxide sample diffuses through the permeation tube wall into the air stream at a known rate, dependent upon temperature. The sulphur dioxide concentration of the gas mixture is thus precisely controlled. It is used to calibrate the analyzer accordingly.
Prior attempts to provide precisely controlled mixing of fluids or dilution of one fluid by another through permeation or diffusion techniques have left much to be desired, however, because of the complexity and expense of the apparatus required, the difficulty in obtaining reproducible results, the limited range of dilution control, and/or the inability to accommodate variations in fluid temperature and flow rate. It has been known that the amount of permeation or diffusion of a fluid through a permeable wall is a function of temperature, but prior attempts to provide precise temperature control of the permeation process have left much to be desired, despite an extensive body of prior art in the heater, heat exchanger, and temperature controller field, including, for example, U.S. Pat. Nos. 2,706,620; 2,446,367; 1,480,922; 3,368,546; 1,906,450; 1,389,166; 2,730,083; 1,519,395; 1,772,557, and 1,624,843.